def yield_read(f, newline):
    buf = ""
    while True:
        while newline in buf:
            pos = buf.index(newline)
            yield buf[:pos]
            buf = buf[pos + len(newline):]
        chrunk = f.read(4096)
        if not chrunk:
            yield buf
            break
        buf += chrunk


with open('1.txt', 'r') as f:
    for line in yield_read(f, ','):
        print(line)
